Numerically controlled system for gear cutting machine

ABSTRACT

The machine is controlled by a selective digital input to provide gear indexing to determine the number of teeth and to provide table movement to control the extent of axial movement required to machine the gear from a gear blank. The numerical input information is provided by a cascaded decade arrangement of binary coded decimal switches to control each of the two necessary functions of head stepping and table stepping movement in both forward and return direction. It is possible to preprogram and to change the degree of accuracy to which the gear cutting is to be carried out by further presetting in the system a digital number representing the number of parts in which the 360* circle representing the gear blank circumference is to be divided.

United States Patent [191 Sieradzki et al.

[451 Feb. 19, 1974 Primary ExaminerB. Dobeck Attorney, Agent, orFirml-lauke, Gifford, Patalidis & Dumont [5 7 ABSTRACT The machine iscontrolled by a selective digital input to provide gear indexing todetermine the number of teeth and to provide table movement to controlthe extent of axial movement required to machine the gear from a gearblank. The numerical input information is provided by a cascaded decadearrangement of binary coded decimal switches to control each of the twonecessary functions of head stepping and table stepping movement in bothforward and return direction. It is possible to pre-program and tochange the degree of accuracy to which the gear cutting is to be carriedout by further presetting in the system a digital number representingthe number of parts in which the 360 circle representing the gear blankcircumference is to be divided.

26 Claims, 5 Drawing Figures NUMERICALLY CONTROLLED SYSTEM FOR GEARCUTTING MACHINE [75] lnventors: Ryszard Sieradzki, Troy; Daniel Goldman,Southfield, both of Mich.

[73] Assignee: Electronic Indexing, Inc., West Bloomfield, Mich.

[22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,554

[52] US. Cl 318/39, 318/571, 318/603 [51] Int. Cl. G05b 19/24 [58] Fieldof Search 318/603, 39, 571, 685, 696

[56] References Cited UNITED STATES PATENTS 3,232,170 2/1966 Findley318/39 X 3,267,344 8/1966 McDaniel 318/39 3,469,495 9/1969 Kelly 318/571X 3,621,357 1 1/1971 Kubo 318/603 X 3,705,339 12/1972 Rhoades 318/39 XFLIP FLIP-1* GATE H026 70 smut FLIP- FLOP/Q3 SINGLE 2 SHOT i Q FLIP-J/Ql I FLOP6 T COUNTER 9i tiara SWITCH DELAY PAIENTEU FEB! elm sum 1 OF5 PAIENI FEB 1 s 1914 SHEET '4 OF 5 NUMERICALLY CONTROLLED SYSTEM FORGEAR CUTTING MACHINE BACKGROUND OF THE INVENTION A number of systems areknown forproviding a numerical control arrangement for gear cutting.Such systems have been devised, for example, for helical thread cuttingsuch as the system shown in U. S. Pat. No. 3,267,344 issued on Aug. 16,1966 for Numerically Controlled Work and Feed Motor Driven Gear- Hopper.

The present invention is particularly directed toward cutting of spurgears, although it is possible by changing the path of relative movementbetween cutter and gear blank to provide different shaped gears such asstraight, bevel or helical. It will be understood that while the presentinvention is particularly adapted for the cutting of gear teeth on agear blank, it is likewise applicable to other systems in which anapproach and return are required, plus a rotary indexing of the partbeing machined. In this way, the basic principles of the invention maybe extended to equipment for sharpening cutters, machining flutes inworkpieces, cutting splines in workpieces and the like.

SUMMARY OF THE INVENTION The present invention will thus be seen toinclude a numerically controlled system with ready provision forchanging the cutting program for a particular workpiece with the digitalinformation preset by thumbwheel binar'y coded decimal switches, greatlysimplifying the initial setup and subsequent changeovers to differentgear types. The numerical control system further makes provision for arapid return during the reciprocating movement of the table carrying thepart being machined, further to speed the machining operation. Thesystem is exceedingly versatile in that it makes provision for changingthe tolerance for the part being machined merely by changing the settingprewired for the number of decimal parts to which the accuracy is to becarried out. All of the various components in the system are either ofthe TTL or DTL type, which represent integrated circuits compatible onewith the other and readily available on the commercial market today.

In the appended specification, reference will be made to exemplary typesof integrated circuits which are suitable for use in connection with thepresent invention, but it will be understood that where these examplesare offered they are meant to be representative and not limiting withrespect to the breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will bedescribed with reference to the following specification and theaccompanying drawings in which like numerals are used to refer to likeparts or components where they may occur in several places in thedrawings and wherein:

FIG. I is a combined block diagrammatic and schematic showing ofmechanical elements and of the digital control system of the presentinvention as it is used to control the travel and indexing of a machinefor cutting gear teeth:

FIGS. 2 through 5 are combined schematic and block diagrammatic drawingsillustrating the several parts of the numerical control system, as wellas the output stage used to control the operation of the stepping motorswhich provide the indexing and then the reciprocating feed movement ofthe machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. I is referred toas showing the basic gear cutting machine which includes a machine baseportion 20 and a machine stationary head portion 22. A rotary gearcutter 24, which may be a conventional milling cutter, is mounted on adriven shaft 26, which shaft in turn is driven through its own drivemotor (not shown). The gear blank 28, which is to be machined, ismounted on a rotatable arbor or work spindle 30 which is rotatablyjournaled through a mounting post 32. The arbor is connected at itsright hand end to the output or drive shaft 34 of a head stepping motor36. It will be understood that the stepping motor 36 is used to rotateor index the gear blank 28 incrementally, for example in acounterclockwise direction as indicated by the arrow A. The amount ofrotation of the gear blank 28 each time will determine the spacingbetween the separate gear teeth being formed and thus the number ofteeth being cut in the periphery of the gear blank 28. It will furtherbe seen that the mounting means for the gear blank 28 is carried on atable 38. The table 38 is movable leftwardly and rightwardly on a pairof machine ways 39 in the direction shown by arrows B through theoperation of a table stepping motor 40.

In a typical gear or spline cutting operation, the individual tooth willbe cut by a leftward motion with a rightward return motion of the table38, followed by an indexing or rotary movement powered by the steppingmotor 36, and then the cycle is repeated. It will be understood that theoutput shaft 42 of the table stepping motor 40 is connected through anintermediate lead screw or similar coupling arrangement to the table 38to precisely control its degree of movement in a leftward or rightwarddirection. The detail of the table 38 driving and connecting mechanismis conventional and has been omitted from this application in theinterest of brevity and simplification.

It will further be seen that the motor 36 is shown both in its physicaloutline and in a schematic designation to clarify the interconnectionbetween the electronic control system and the motor. In a like manner,the table stepping motor a0 is shown in both its schematic designationand in its physical outline. The portion of the electronic controlsystem which operates to control the head indexing movement and hencethe number of teeth being cut is located at the lower left hand portionof the FIG. I drawing and is indicated generally by the numeral 48. Theportion of the electronic control system related to the table indexingcontrol which is somewhat less complex is located at the lower righthand portion of the drawing of FIG. 1 and is identified by the numeral50.

Now, with reference to the system for controlling the number of teeth tobe machined, included is a thumb wheel switch 52 which is used toprovide a binary coded decimal input for a following binary codeddecimal counter 54. This counter usually includes three decades withfour switches for each decade. The second working counter is identifiedby the numeral 56. The counter 56 likewise includes three binary decadecounters as will be shown in greater detail in FIG. 3 hereinafter.

Also included in the system for controlling head indexing are the uppercounters 58 and 60. The counter 58 has been wired into the system andactually determines the number of even parts into which the circle, thatis the circumference of the gear blank, will be divided. According tothe number of decade stages and digits included in the counter 58, theaccuracy is determined. The counter 58 is initiated in its operation bythe cycle start switch 62 and associated flip-flop 64 and by the controloutput from these elements. The counter 60 is controlled in itsoperation by the control flip-flop 64 and and through an intermediateflip-flop 68 and a gate 70, which gate controls the input or clockpulses from a free-running clock pulse source 72 through a sequencer 66.The sequencer 66 in turn is controlled by the output of a gate 74. Afurther flip-flop 76 is includes in the system to ready the indexingsection for operation at the end of each cutting pass of the machinetable 38.

The output from the counter 60 is effective through intermediatesingle-shot 78 and flip-flop 80 and the following stages to control theoperation of the head stepping motor 36. Included in the pulse inputchannel for the head stepping motor 36 is a separate free-running clock82, a gate 84 and a final input stage comprising a dual flip-flop 86. I

As previously stated, the control system for the table stepping motor 40is included at the lower right hand portion of the circuit and indicatedgenerally by the numeral 50. There is provided a thumbwheel switch 88 toselectively set the length of table travel required in increments ofdecimal parts of an inch as for an input for a separate decade counter90. The decade counter 90 is connected to a pulse output from anup-and-down counter 92 through a single-shot 94 and a gate 96. A sourceof pulses for driving or stepping the table stepping motor 40 isprovided from a further free-running clock pulse source 98, a gate 100and a final dual flipflop 102. The single shot 94 performs the functionof operating the flip-flop 80 and resetting the gate 84 so that the gatewill pass no further pulses to the head stepping motor 36. The gate 97once reset will permit the free-running clock 98 to send the pulses todrive the table stepping motor 40.

Also included in the circuit is a flip-flop 104 which when reset willpermit the table stepping motor 40 to count in the opposite direction.For example, if the count in the counter 90 has first been counted downrightwardly, it will then be counted down leftwardly except that on thereturn a rapid return movement is employed. A delay stage 106 isconnected to the circuit to provide an output to set a followingflip-flop 108, which in turn energizes a single-shot multivibrator 110,which in turn sets again theflip-flop 76. This enables the sequencer 66to pass pulses from the free-running clock 72 and start the process overagain with the next following indexing movement of the head steppingmotor control system 48. The system for operating the motors 36 and 40,as shown in FIG. 1, will be fully described in the Description ofOperation" hereinafter after due consideration has been given to thevarious circuit IC components and their mode of interconnection.

FIGS. 2, 3, and the upper portion of FIG. 4, show the detailed schematicof the electronic digital control system for operating the head steppingmotor 36. Inverters, identified by the conventional symbol, areconnected in the circuit as required. Included in this system are thethumbwheel switches 54 which select by their setting the number of teethto be cut in the periphery ofthe gear blank 28. Once they have been set,these switches further afford a visual display of the conditions underwhich the gear cutting machine is being operated. A separate counter 56is controlled in accordance with the settings made on the counter 54.The counters 58 and 60 are shown at the upper part of the FIG. 3 drawingand represent a five digit cascaded decade counter with the decimalsetting representing the number of parts into which the gear blank is tobe cut. As an exemplary setting, 20,000 has been prewired into thecounter 58. This number is transferred into the counter 60 which is aworking counter during a cycle of operation. It is preferable thatintegrated circuits or ICs be used for economy, compactness of designand reliability of operation. One example of a decade counter suitablefor use in the present invention for counters 54 and 56 is the up-downdecade counter Model DM8560 currently manufactured and sold by theNational Semiconductor Coporation of Santa Clara, Calif. Similar typedecade counters may be used in the counter 92 shown in FIG. 4, which issubsequently employed to count up and down and then initiate thestepping of the table 38 through the operation of the table steppingmotor 40.

FIG. 2 shows the cycle start switch 62 and the next following controlflip-flop 64. The control flip-flop 64 may comprise for example, anupper triple input gate and a lower input gate. these may be embodied byway of example with integrated circuits Models MC862-P and MC846-P nowmanufactured and sold by the Motorola Corporation of Phoenix, Ariz. Itwill bbe understood that these particular ICs can be used as buildingblocks for a great number of the system components to be describedhereinafter.

The function of the flip-flop 64 is to provide a transfer of theinformation preset in the thumbwheel switches 54 to the decade counter56 preparatory to the cycle of operation. Information for the uppermostdecade counter 58 of FIG. 3 has already been prewired for 20,000 asindicated numerically on the box representation for the counter 58. Atthe same time, the flipflop 64 will be presetting the flip-flop 76,which in turn enables the gate 74. The gate 74 operates as a gate forthe output of the free-running clock 72. It will be understood that theclock 72 may be comprised of a pair of monostable flip-flops 72a, 72bsuch as, for example, flip-flop Model MC85 l-P currently commerciallyavailable from the Motorola Corporation of Phoenix, Ariz.

The pulse output from the clock 72 when passed through the gate 74serves to operate the sequencer 66. Included in the sequencer 66 are twostages a binary coded decimal counter 66a and a converter 66b forconverting the binary coded decimal to a straight decimal output.Integrated circuits suitable for use in the sequencer 66 are, forexample, Models Sn7490 and Sn7442 currently manufactured and sold bySignetics Corporation of Sunnyvale, Calif. It will be seen that thefirst pulse output from the sequencer 66 is fed back to the controlflip-flop 64 to set it, so that if the operator desires to set the cycleagain the flip-flop 64 will be in the proper condition. The next pulseoutput from the sequencer 66 is passed through a subsequent flip-flop 68and a gate to provide the function of transferring the informationprewired into the upper decade counter 58 into the lower decade counter60. There is provided a third output pulse from the sequencer 6,6, whichoperates to set the next flip-flop 68 so that the pulses originatingfrom the clock pulse source 72 are allowed to pass through tthe gate 74.The pulses from the clock 72 are thus permitted to pass to both thecounter 60 and the counter 56. It will be understood that when the firstflip-flop 64 was reset, the information preset in the counter 54 wasbeing transferred to the counter 56 in a like manner as to the transferof informaion between counters 58 and 60, already referred Alsoconnected in the circuit is a single shot 57 which performs theoperation of resetting the counter 54 to its orginal condition and alsoresetting the counter 58 to its original condition. Each time a numberis being subtracted from the preset entry, that pulse is also being fedto a through gate 59 following counter 92, the detail of which is bestshown in the lower portion of the FIG. 4 drawing. An additional singleshot multivibrator 78 is used to activate the gate 84 through theoperation of the flip-flop 80. The gate 84 controls the output from asecond free-running clock 82. The actual drive circuit or the headstepping motor 36 is provided by a dual flip-flop stage 86. The dualflip-flop 86 may be embodied as a dual JK flip-flop Model MC853-Pcurrently manufactured and sold by the Motorola Corporation of Phoenix,Ariz.

An amplifier stage for the motor 36 drive is transistor stage 87.Included in the stage 87 are a pair of transistors 87a and 87b. Anemitter resistor 89 is included in the circuit and a 1I 9 is neudedfetre qle tion. The controlcoils for the head stepping or indexingmotor 36 are shown and the respective terminals are numbered x, y, z,and w. The stepping motor 26 is operated through a predeterminedsequence of its coils, which is, for example x,y; y,z; z,w; w,x; andcycle is repeated so that two coils are energized and two coils at thesame time are deenergized to provide stepping of the motor 36 in onedirection.

If the stepping motor, such as motor 40, is to be operated in theopposite direction, the sequence is simply reversed.

A similar drive arrangement with a drive stage 87 and a pair oftransistors 87a and 87b is shown for the table stepping motor 40 at thelower right hand portion of the FIG. 5 drawing. It will be understoodthat the single shot multivibrator 94 coupled to the output of thecounter 92 has a dual function: that of resetting the gate 84 at the endof the indexing part of the cycle to inhibit further pulses to the headstepping motor 36, and at the same time activating the gate 97 so thatthe pulses from the free-running clock source 98 are then permitted todrive the stepping motor 40 so that table feed is initiated. Thus, theoperation performed is changed over between head indexing of the gearblank 28 through the head stepping motor 36 and table feeding of thetable 38 through the table stepping motor 40. Once the gate 97 has beenactivated, the pulses are passed from the free-running clock pulsesource 98 and through to the stage 102 to provide the table steppingoperation through the stepping motor coils in the manner just indicatedfor the head stepping motor 36. The presetting of the travel distance ofthe head 38 is provided by the setting of the switches 88, whichpreferably are thumbwheel switches, allowing a visual indica tion of thedistance being preset for table travel. The

counter stage provides for a division of the total distance into decimalinches. One type of counter appro priate for use in the counter stage 90is the decade counter Model SN7490 commerically manufactured and sold bySignetics Corporation of Sunnyvale, Calif. It is important that thetable 38 travel be provided first in one direction for the cuttingstroke and then in the opposite direction for the return stroke. As thecountdown occurs in the counter 90, it is also resetting the flip-flop104. The flip-flop 104 when reset allows the table stepping motor 40 tocount in an opposite direction so that if the initial travel was to theright it will now be the same distance to the left, except that thistime the travel will occur at a much faster rate, that is, with a rapidreturn. This time when the correct count is repeated there will beprovided an output pulse from a delay line 106, which will becommunicated through the flip-flop 108 and single shot 110 to reset theHip flop 76 and start the operation of the sequencer 66 to repeat thehead index cycle of operation again.

As shown in FIG. 5, the table stepping motor 40 has its coil terminalslettered R, S, T and U and it will be understood that for a forwardoperating sequence the coils will be energized R-S, S-T, T-U and U-R andthe cycle will be repeated. In opposite direction travel, this sequencewill be reversed. It will be seen that there are included in the circuita pair of OR gates 107 as inputs to the dual flip-flop 102. The OR gates107 may be embodied as two input OR gates, such as Model MCI 8l2-Pcurrently manufactured and sold by Motorola Corporation of Phoenix,Ariz. This portion of the circuit controls the coil sequencing of themotor 40 in its forward and reverse operation.

DESCRIPTION OF OPERATION The operation of the control system accordingto my invention will now be described, giving particular at tention tothe block diagram of FIG. 1 and the schematic of FIG. 3. The thumbwheelswitch 52 has preset on it the number of teeth which are to be cut inthe gear 28. The degree of accuracy is prewired into the counter 58 withthe setting being made representative of the number of even parts intowhich the circle representing the circumference of the gear blank willbe divided. The operator also will have preset the thumbwheel switch 88to predetermine the amount of travel of the table 38 which carrier thegear blank 28 through a cutting stroke by the rotary cutter 24. It willbe obvious to one skilled in the machine tool art that with anappropriate change of the machine tool elements, the cutting stroke maybe accomplished by maintaining the gear blank 28 and the spindle 30stationary and moving the milling cutter 24 in a suitable cutting pathof travel. The distance of travel may, by way of example, be presettablebetween 2 and 5 inches with each inch being divided into thousandths ofan inch.

It will be noted that in FIGS. 2-5 there are a number of reset terminalsidentified IR, which are provided with a reset pulse so that all of theflip-flops, such as flip-flops 104, 64, 76 and the other flip-flops inthe system will be initially reset in the condition required. Anappropriate single reset pulse is thus provided for the reset of theflip-flops at the beginning of the operation.

In the operation of the system, once the number of teeth have beendialed in and the table travel distance has been dialed, the operatorthen operates the cycle start switch 62 which sets the flip-flop 64. Thelowermost output from the flip-flop 64 then serves to transfer fromcounter 54 to counter 56 the infor-' mation that has been previously setby the operator in counter 54 through the thumbwheel switch 52. At thesame time, the prewired setting in the upper counter 58 is transferredinto the working counter 60. In the numerical example we have chosen,the circuit was divided into 20,000 even parts. At the same time, thereis provided an output to the flip-flop 76 to set it and enable the gate74 th1 1s to provide passage of the clock pulses from the freerunningclock 72. The sequencer 66 is provided with a binary coded input aspreviously described. The first pulse output from the sequencer 66 isused to reset the flip-flop 64 to permit restart by the operator if heso desires.

The second pulse from the sequencer 66 is used to transfer informationalready transferred. by the flip-flop v 64 to the counter 58 to thecounter 60. The next pulse is used to reset the flip-flop 68, whichturns on or enables the gate 70 so that the clock pulses pass into thecounters 60 and 56. After the number of pulses are received as preset inthe counter 56, the single shot 57 enables the gate 59, at the same timeresetting the counter 56. The information is also being passed on to thecounter 92. After the count in the counter 56 has been transferred tothe counter 92, the count in the counter 60 will operate a single shotmultivibrator 78 which will enable the gate 84 through flip-flop 80.Thus, the free-running clock pulses from clock 82 will be passed throughthe dual flip-flop 86 and the associated drive stage 87, as shown inFIG. 4, to step the head stepping motor 36 the required number of steps.

When the number preset and transferred to the counter 92 has returned tozero, the single shot multivibrator 94 will be activated to provide apulse output to flip-flop 104, gate 96 and gate 97. The gate 84 willthus be reset to inhibit the passage of any more pulses from the clock82 to step the motor 36. At the same time, the table travel is initiatedby activating of the gate 97 and gate 100 to provide clock pulses fromthe clock 98 to pass and drive the flip-flop 102 and the associateddrive circuit 87 as shown in FIG. 5. After the correct number of pulseshas passed to move the table 38 in accordance with the presetting on thethumbwheel switch 88, the counter 90 will reset. The flip-flop 104 willthen be switched which will then provide counting and the stepping ofthe stepping motor 40 in an opposite direction. When the right count isagain sensed, the output pulse will be passed from the counter 90 to thedelay 106. The delay pulse output from the delay stage 106 is thenpassed to reset the flip-flop 1108 and activate the single shot 110,thus resetting the flip-flop 76 to permit another indexing cycle ofoperation through the sequencer 66 as previously described.

The entire process set forth above will be repeated for as many times asthe thumbwheel switches 52 have been set. in our exemplary embodiment,the cycle will be repeated five times. Each time the decade counter 60will count down until all 20,000 pulses have been counted. When thecounter 58 is finally counted down to zero, the flip-flop 76 will bereset for the last time. in accordance with our example, if the counter58 is preset at 20,000 and the thumbwheel switches 52 and therefore thecounter 54 are set at five, then the division will be performed in suchmanner that 20,000 will be divided by five. This will leave a 4,000pulse count which will actually be transferred into the counter 92 andthis will be the number of pulses which the system will step the headstepping motor 36 in one direction. These 4,000 steps are also beingsubtracted from the total of 20,000 in the counter 58. At the same time,the number one is subtracted from the five preset in the counter 54 toreduce it to four. At the end of the first indexing operation, thecounter 58 has been reduced to 16,000 and the counter 54 has been setback to four. At the end of the next cycle of operation, the count leftin the counter 58 is 12,000 and the count left in counter 54 is three.Each time, the table 38 is moving leftwardly-rightwardly to return. Thenext index is set so that the 12,000 has been divided by three and wehave another 4,000 pulses which are passed to the counter 92 and thencepassed to step the motor 36. in the final operation, there is a count of4,000 left in the counter 58 which is divided by one left in the counter54. This gives a 4,000 count which is then subtracted from the counter58, leaving it with a zero count. At this point, a pulse output from thecounter 58 blocks the flip-flop 108 so that no more counting can occuruntil another complete cycle is started by cycle start switch 62.

it will thus be seen that the present invention offers the capability ofready changeover as the accuracy of the operation needs to be increasedor decreased. By simply dropping off the final decade stages, of, forexample, counters 58 and 60, the accuracy can be reduced to a lowerlevel required. In the event a more accurate machining operation isrequired, additional decade stages can be switched in for the counters58 and 60. it will be understood that external capacitors may be addedas necessary, for example, such as capacitors 98c and 98d in the clockstage 98 (H0. 5) or 820 and 82d in the clock stage 82 (FIG. 4), toadjust the frequency of operation. The purpose of the delay line 106isto make sure that there is acompletion of the table indexing travelbefore the next indexing crsleisisfiiated;

It will thus be seen that l have provided by the present invention anextremely versatile and accurate electronic control system for cuttinggear teeth or the like in a workpiece. The invention is applicable toany type of machining apparatus in which a precise, digitally controlledmovemen of the headpiece and a similar precisely controlled movement ofthe table are needed. Changeover of operation with respect to the numberof gear teeth and the cutting stroke can be readily made by the settingof the two thumbwheel switches, thus giv' ing a visual indication of theexact settings in which machining is being carried out.

What is claimed is:

1'. An electronic control system of the digital type for providing aprecision rotary indexing movement of a part to be machined comprising:

a rotatable mounting means for said part;

a stepping motor having its output operatively connected to saidmounting means for providing an incremental rotary movement of saidpart;

a first counter preset in accordance with the number of incrementalsteps into which a full circle rotary movement of said part is to bedivided;

a second counter;

a manually operated means for presetting said second counter inaccordance with the number of separate indexing positions into which thepart is to be turned;

means for dividing the first number preset in said first counter by thenumber preset in the second counter;

means for deriving a pulse train representative of the digital value ofthe quotient;

drive means for converting the pulse train into a plurality of steppingpulses for said stepping motor; and

means for providing a feed and return stroke of said part in an axialdirection at the end of each operation of said drive means.

2. The combination as set forth in claim 1 wherein said last mentionedmeans comprises a second stepping motor and a digital control meanspresettable with a number representative of the distance of travelrequired for said table.

3. The combination as set forth in claim 2 wherein an intermediateup-down counter is included in said system for initiating the operationof said second stepping motor subsequent to each completion of operationof said drive means.

4. The combination as set forth in claim 3 wherein said second countercomprises a multiple decade counter and said manually operated meanscomprises a thumbwheel switch operable to provide a predetermined binarycoded decimal input to said scccond counter.

5. The combination as set forth in claim 1 wherein said part is mountedon a spindle coupled to the output of said stepping motor and said meansfor providing a feed and return stroke of said part comprises a tablemovable on ways parallel to the axis of said part.

6. The combination as set forth in claim 3 wherein said first and secondstepping motors are operated by different clock sources, each having aselectively variable frequency of operation.

7. A digital control system for cutting teeth in a gear blank includinga stepping motor for indexing the blank in a rotary manner to aplurality of tooth cutting positions and a second motor for providing atimed cutting stroke and relative movement between the blank and analigned cutter means, comprising a first counter preset in accordancewith the number of parts into which the gear blank periphery is to bedivided;

a second counter selectively preset with the number of teeth to be cutinto the gear blank; means for dividing the first number by the secondnumber and providing a pulse output equal to the quotient resulting fromthe dividing operation; and

gating means for passing said number of pulses to said stepping motorfor controlling its incremental movement between successive toothcutting positions.

8. The combination as set forth in claim 7 wherein said second counterhas associated with it a plurality of manipulatable switches forselectively presetting it in the number representing the number of teethto be cut.

9. The combination as set forth in claim 8 wherein said first counterincludes a plurality of cascaded decade stages of the number of partsinto which the gear blank circumference is to be divided.

10. The combination as set forth in claim 7 wherein said gear blank ismounted on a table reciprocably movable by said second motor in amachining pass and wherein said cutter comprises a milling cuttermounted in a stationary position relative to said gear blank.

11. The combination as set forth in claim 7 wherein said gear blank ismounted in a stationary position relative to movement in an axialdirection and wherein said cutter comprises a milling cutter movableaxially relatively to said gear blank during a gear cutting pass.

12. The combination as set forth in claim 10 wherein said second motorcomprises a stepping motor for pro viding a precisely controllablemovement of said table relative to said gear blank and wherein a furthercounter means and a plurality of manually operable switches associatedwith said counter are used to control the incremental degree of movementof said table in its feed and return direction.

13. The combination as set forth in claim 12 wherein said movement in aforward cutting direction is at a substantially slower rate than thereturn feed movement of said table.

14. The combination as set forth in claim 12 wherein a gating means isconnected intermediate said counters controlling the incrementalindexing of said blank and said second motor controlling thereciprocating movement whereby the forward and rearward stroke of saidblank relative to said cutter is initiated at the end of each toothindexing movement.

15. The combination as set forth in claim 14 wherein a pair of clockpulse sources are included, one for said first group of counters and onefor said second counter controlling the feed stroke whereby the feed andreturn of said cutter may be varied selectively and independently of thespeed of operation of said stepping motor controlling the gear blankindexing.

16. The combination as set forth in claim 15 wherein said clock pulsesources comprise multivibrators of the integrated circuit type, eachhaving its frequency of operation variable by the connection of anexternal capacitor.

17. A digital control system for cutting teeth in a gear blank includinga first stepping motor for indexing the blank in a rotary manner to aplurality of tooth cutting positions and a second stepping motor forproviding a timed cutting stroke movement of the blank relative to astationary cutter, said system comprising:

a first counter preset in accordance with the number of parts into whichthe gear blank circumference is to be divided;

a second counter selectively preset with the number of teeth to be cutinto the gear blank;

means for dividing the second number by the first number and providing adigital representation of the quotient;

a third counter for storing said digital representation of the quotient;

driving means for said first stepping motor for providing a digitalstepping movement of said first motor responsive to the count stored insaid th rtls t tt s t gating means for ensuringureaaaanm ors'iim'c ondstepping motor responsive to the count to zero of said third counter.18. The combination as set forth in claim 17 wherein a fourth counter isincluded in the system for controlling the feed of said second steppingmotor, said system including a manipulatable switching means forpresetting it to determine the extent of movement of said secondstepping motor in a forward stroke, and a flip-flop connected to saidfourth output for initiating a like distance return stroke following thecompletion of said forward stroke.

19. The combination as set forth in claim 18 wherein a gating means isoperably connected intermediate said first counter and said fourthcounter for providing a forward and return movement by said secondstepping motor after each cycle of operation of said first steppingmotor.

20. The combination as set forth in claim 17 wherein each of saidcounters is coupled to a clock of the integrated circuit type havingterminals for coupling an external capacitor for adjusting its frequencyof operation.

21. The combination as set forth in claim 17 wherein said means forpresetting said second counter comprises a binary coded decimal typethumbwheel switch for providing a visual indication of the parameters ofthe gear cutting operaioni 22. The combination as set forth in claim 17wherein a separate free-running clock pulse source is operably connectedto each of said counters for providing separate time controlledoperation of each of the respective counters. v

23. The combination as set forth in claim 22 wherein said gear blank ismachined by a stationary cutter rotatably mounted in cuttingrelationship proximate its path of travel and wherein said gear blank isfixed to an arbor, said arbor mounted on a table axially movable underthe control of said second stepping motor.

24. The combination as set forth in claim 23 wherein said secondstepping motor is movable at a predetermined speed during the feedoperation and movable at a somewhat more rapid rate of movement in itsreturn stroke. if

25. The combination as set forth in claim 17 wherein said driving meanscomprises a dual JK flip-flop having its output coupled to said firstmotor for energizing its coils in a predetermined sequence to providesaid movement.

26. The combination as set forth in claim 18 wherein a driving means isincluded for said second motor, said driving means comprising a dual JKflip-flop havingits output coupled to the coils of said motor forenergizing its coils in a predetermined sequence to provide said forwardstroke and for energizing its coils in a reverse sequence to providesaid return stroke.

Patent No.

Dated February 19,

Inventor(s) Col. 3,

Col. 4,

Col. 5,

Col. 6,

Col. 7,

Ryszard Sieradzki and Daniel Goldman It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

line

line 13, after "input", delete "or" and insert of;

line l7, delete "includes" and insert --included-.

line 2l, delete "Cpporation" and insert Corp'oration-;

line 33, delete "bee" and insert -be-;

line 34, delete "ICs" and insert ICs-;

lines 64-66, delete "is passed through a subsequent flip-flop 68 and agate 70 to provide the function of transferring" and insert -transfers-.

line "tthe" should read the line 5, delete "74" and insert 70;

line 11, delete "informaion" and insert -information 14, delete "54" andinsert -56-;

line 24, delete "or and insert-for-;

line 47, delete "carrier" and insert -carries--.

line 62, delete "When" and insert After the flipflop 76 will be resetfor the last time-;

ORM PO-IOSO (IO-69) USCQMM-DC 50376-P59 i U.S, GOVERNMENT PRINTINGOFFICE: I969 0-356-334 Patent N 3,793,575 D d February 19, 1974lnventofls) Ryszard Sieradzki and Daniel Goldman I It is certified thaterror appears in the above-identified patent and that said Letters.Patent are hereby corrected as shown below:

- Page 2 Col. 7, line 63, delete "the flip-flop 76 will be reset for thelast time";

Col. 8, line 46, delete "movemen" and insert -movement.

Col. 9, line 26, delete "seccond" and insert -second.

Col. 10, line 67, after "fourth", insert -counter.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN .Attesting Officer Commissioner ofPatents ORM F'O-IOSO (10-69) I o 60376.;259 t 11.5. GOVERNMENT PRINTINGOFFICE: 1969 0-365-334

1. An electronic control system of the digital type for providing aprecision rotary indexing movement of a part to be machined comprising:a rotatable mounting means for said part; a stepping motor having itsoutput operatively connected to said mounting means for providing anincremental rotary movement of said part; a first counter preset inaccordance with the number of incremental steps into which a full circlerotary movement of said part is to be divided; a second counter; amanually operated means for presetting said second counter in accordancewith the number of separate indexing positions into which the part is tobe turned; means for dividing the first number preset in said firstcounter by the number preset in the second counter; means for deriving apulse train representative of the digital value of the quotient; drivemeans for converting the pulse train into a plurality of stepping pulsesfor said stepping motor; and means for providing a feed and returnstroke of said part in an axial direction at the end of each operationof said drive means.
 2. The combination as set forth in claim 1 whereinsaid last mentioned means comprises a second stepping motor and adigital control means presettable with a number representative of thedistance of travel required for said table.
 3. The combination as setforth in claim 2 wherein an intermediate up-down counter is included insaid system for initiating the operation of said second stepping motorsubsequent to each completion of operation of said drive means.
 4. Thecombination as set forth in claim 3 wherein said second countercomprises a multiple decade counter and said manually operated meanscomprises a thumbwheel switch operable to provide a predetermined binarycoded decimal input to said seccond counter.
 5. The combination as setforth in claim 1 wherein said part is mounted on a spindle coupled tothe output of said stepping motor and said means for providing a feedand return stroke of said part comprises a table movable on waysparallel to the axis of said part.
 6. The combination as set forth inclaim 3 wherein said first and second stepping motors are operated bydifferent clock sources, each having a selectively variable frequency ofoperation.
 7. A digital control system for cutting teeth in a gear blankincluding a stepping motor for indexing the blank in a rotary manner toa plurality of tooth cutting positions and a second motor for providinga timed cutting stroke and relative movement between the blank and analigned cutter means, comprising a first counter preset in accordancewith the number of parts into which the gear blank periphery is to bedivided; a second counter selectively preset with the number of teeth tobe cut into the gear blank; means for dividing the first number by thesecond number and providing a pulse output equal to the quotientresulting from the dividing operation; and gating means for passing saidnumber of pulses to said stepping motor for controlling its incrementalmovement between successive tooth cutting positions.
 8. The combinationas set forth in claim 7 wherein said second counter has associated withit a plurality of manipulatable switches for selectively presetting itin the number representing the number of teeth to be cut.
 9. ThecOmbination as set forth in claim 8 wherein said first counter includesa plurality of cascaded decade stages of the number of parts into whichthe gear blank circumference is to be divided.
 10. The combination asset forth in claim 7 wherein said gear blank is mounted on a tablereciprocably movable by said second motor in a machining pass andwherein said cutter comprises a milling cutter mounted in a stationaryposition relative to said gear blank.
 11. The combination as set forthin claim 7 wherein said gear blank is mounted in a stationary positionrelative to movement in an axial direction and wherein said cuttercomprises a milling cutter movable axially relatively to said gear blankduring a gear cutting pass.
 12. The combination as set forth in claim 10wherein said second motor comprises a stepping motor for providing aprecisely controllable movement of said table relative to said gearblank and wherein a further counter means and a plurality of manuallyoperable switches associated with said counter are used to control theincremental degree of movement of said table in its feed and returndirection.
 13. The combination as set forth in claim 12 wherein saidmovement in a forward cutting direction is at a substantially slowerrate than the return feed movement of said table.
 14. The combination asset forth in claim 12 wherein a gating means is connected intermediatesaid counters controlling the incremental indexing of said blank andsaid second motor controlling the reciprocating movement whereby theforward and rearward stroke of said blank relative to said cutter isinitiated at the end of each tooth indexing movement.
 15. Thecombination as set forth in claim 14 wherein a pair of clock pulsesources are included, one for said first group of counters and one forsaid second counter controlling the feed stroke whereby the feed andreturn of said cutter may be varied selectively and independently of thespeed of operation of said stepping motor controlling the gear blankindexing.
 16. The combination as set forth in claim 15 wherein saidclock pulse sources comprise multivibrators of the integrated circuittype, each having its frequency of operation variable by the connectionof an external capacitor.
 17. A digital control system for cutting teethin a gear blank including a first stepping motor for indexing the blankin a rotary manner to a plurality of tooth cutting positions and asecond stepping motor for providing a timed cutting stroke movement ofthe blank relative to a stationary cutter, said system comprising: afirst counter preset in accordance with the number of parts into whichthe gear blank circumference is to be divided; a second counterselectively preset with the number of teeth to be cut into the gearblank; means for dividing the second number by the first number andproviding a digital representation of the quotient; a third counter forstoring said digital representation of the quotient; driving means forsaid first stepping motor for providing a dgital stepping movement ofsaid first motor responsive to the count stored in said third counter;and gating means for enabling the operation of said second steppingmotor responsive to the count to zero of said third counter.
 18. Thecombination as set forth in claim 17 wherein a fourth counter isincluded in the system for controlling the feed of said second steppingmotor, said system including a manipulatable switching means forpresetting it to determine the extent of movement of said secondstepping motor in a forward stroke, and a flip-flop connected to saidfourth output for initiating a like distance return stroke following thecompletion of said forward stroke.
 19. The combination as set forth inclaim 18 wherein a gating means is operably connected intermediate saidfirst counter and said fourth counter for providing a forward and returnmovement by said second stepping motor after each cycle of operation ofsaid first stepping motor.
 20. The combination as set forth in claim 17wherein each of said counters is coupled to a clock of the integratedcircuit type having terminals for coupling an external capacitor foradjusting its frequency of operation.
 21. The combination as set forthin claim 17 wherein said means for presetting said second countercomprises a binary coded decimal type thumbwheel switch for providing avisual indication of the parameters of the gear cutting operaion. 22.The combination as set forth in claim 17 wherein a separate free-runningclock pulse source is operably connected to each of said counters forproviding separate time controlled operation of each of the respectivecounters.
 23. The combination as set forth in claim 22 wherein said gearblank is machined by a stationary cutter rotatably mounted in cuttingrelationship proximate its path of travel and wherein said gear blank isfixed to an arbor, said arbor mounted on a table axially movable underthe control of said second stepping motor.
 24. The combination as setforth in claim 23 wherein said second stepping motor is movable at apredetermined speed during the feed operation and movable at a somewhatmore rapid rate of movement in its return stroke.
 25. The combination asset forth in claim 17 wherein said driving means comprises a dual JKflip-flop having its output coupled to said first motor for energizingits coils in a predetermined sequence to provide said movement.
 26. Thecombination as set forth in claim 18 wherein a driving means is includedfor said second motor, said driving means comprising a dual JK flip-flophaving its output coupled to the coils of said motor for energizing itscoils in a predetermined sequence to provide said forward stroke and forenergizing its coils in a reverse sequence to provide said returnstroke.